The Confederate invasion of Pennsylvania ends when Lee's troops slip away across the Potomac in the night

The retreating Confederates had reached the Potomac the week before and found it flooded and impassable. They took up powerful positions between Williamsport and Falling Waters, Maryland on the northern side. Union General Meade's pursuing Army of the Potomac did not attack hastily but gathered forces, including a powerful flanking movement, The floods, however, abated enough for General Lee's troops to slip away across the Potomac during the night of July 13-14, 1863, ending the Confederate campaign into Pennsylvania.  (By John Osborne).